1. Field of the Invention
The present invention relates to a stabilizer combination for use in vinyl halide resins.
2. Description of the Prior Art
While it is generally known to mix hindered phenolic-type antioxidants and organotin stabilizers in polymers, a close examination of the prior art often reveals a fairly specific teaching of which types of antioxidants, stabilizers, and polymers to use:
U.S. Pat. Nos. 3,424,712 and 3,424,717 to J. B. Gottlieb et al. teach use of a vinyl resin substrate with tin stabilizers and monophenol antioxidants, optionally with a third tin-sulfur stabilizer (as covered in the '717 patent).
U.S. Pat. No. 3,759,966 to P. D. Morton et al. teaches use of polymeric tin mercaptides with monohydric phenol, bisphenol, tris-phenol, or tetrakis-phenol stabilizers in vinyl halide resins. This reference distinguishes its polymeric tin mercaptides from conventional monomeric tin mercaptides of the formula R.sub.2 Sn(SR').sub.2 by stressing the polymeric structure of the tin mercaptide as giving these compositions the benefits of lower volatility, lower migration, and lower leaching rates.
U.S. Pat. Nos. 3,442,806 and 3,530,069 indicate that admixtures of a hindered phenolic antioxidant and a dihydrocarbyl tin sulfide of the formula R.sub.2 Sn.dbd.S, where R is alkyl, cycloalkyl, aralkyl and/or aryl, can be used to stabilize organic material. The tin sulfide reactant proposed is a specific class of trifunctional tin sulfide wherein only three moieties are attached to the tin atom, i.e., the two R groups and the sulfur atom which is bonded to the tin atom by a double bond. The trifunctional tin sulfides shown in this patent may be capable of forming trimers wherein the tin atoms have four ligands attached thereto. However, such species are not to be considered to be monomeric organotin compounds.
Other references which show halogen-containing resins stabilized with organotin compounds and phenolic antioxidants are: U.S. Pat. No. 3,609,120 (shows use of mono- and bisphenols as optional, but preferred additives); U.S. Pat. No. 4,274,999 (shows use of orthodihydric phenols); and Japanese Patent Publication No. 60/197,753 (shows use of ortho-divalent phenols which may also have one or more dihydric phenolic ligands substituted thereon).